1. Field of the Invention
This invention relates to a biodegradable resin molded article and to a method of recovering resources. More particularly, the present invention relates to a biodegradable resin molded article usable when durability is required, and a method of recovering resources.
2. Description of the Related Art
Biodegradable resins which are completely decomposed and digested by bacteria in the soil have drawn increasing attention recently with an increase in awareness of the earth's environment.
Several patent applications have already been filed for molded articles using such a resin (e.g. Japanese Unexamined Patent Publication (Kokai) Nos. 3-290461, 4-146952 and 4-325526). These molded articles are used particularly as a film or a packaging material, and durability is not required.
However, it is expected that recovery of durable consumer goods such as electric products, computers, and so forth, will be required in the near future, and research and development has therefore been under way to obtain a material for casings, etc., which can be decomposed. Biodegradable resins are believed to be advantageous in this aspect because decomposition treatment of the recovered molded articles can be carried out at a relatively low cost. To use a molded article as a durable material, it must have sufficient strength and durability. However, a degradable resin which has satisfactory degradability, strength and durability for application as a durable material has not yet been known at present.
In the case of an electric circuit substrate used for electronic appliances, a thermosetting resin is used in most cases with the exception of inorganic materials such as ceramics, and wiring is formed on the substrate surface. It is very difficult to melt and fuse the thermosetting resin. To separate and recover wiring metals, a complicated process is necessary. Further, because the thermosetting resin of the electric circuit substrate does not have decomposability, it remains semi-permanently at the site where it is disposed of and buried.
From the aspect of saving of resources, on the other hand, it is necessary not only to separate the materials but also to recover raw materials.
Since the biodegradable resin is decomposed by bacteria (e.g., mold), it is likely to be degraded or decomposed by bacteria during its use. Therefore, the field of application has been limited to disposable items such as dust bags. To use the biodegradable resin for a long time, degradation by bacteria must first be restricted. Therefore, an attempt has been made to retard biodegradation of the resin by adding an antibiotic (Japanese Unexamined Patent Publication (Kokai) No. 5-51073).
However, the direct addition of the antibiotic to the biodegradable resin involves the problem that control of emission of the antibiotic is difficult. In other words, if emission of the antibiotic occurs too quickly, the effect of the antibiotic will be insufficient. If it is too slow, on the other hand, the period before the start of biodegradation will become too long.